SET TRANSACTION READ ONLY executed in a function has no effect

--source include/have_innodb.inc

--echo #

--echo # MDEV-39542 Assertion failed in trx_flush_log_if_needed()

--echo #

CREATE TABLE t (id INT) ENGINE=InnoDB;

INSERT INTO t VALUES (1),(2),(3);

--delimiter //

CREATE FUNCTION f(i INT) RETURNS INT

BEGIN

SET TRANSACTION READ ONLY;

RETURN i;

END //

--error ER_COMMIT_NOT_ALLOWED_IN_SF_OR_TRG

CREATE FUNCTION g(i INT) RETURNS INT

BEGIN

START TRANSACTION READ ONLY;

RETURN i;

END //

--delimiter ;

DELETE FROM t WHERE id=f(1);

# FIXME: The SET TRANSACTION READ ONLY in f(1) was ignored!

DELETE FROM t WHERE id=2;

SET TRANSACTION READ ONLY;

--error ER_CANT_EXECUTE_IN_READ_ONLY_TRANSACTION

DELETE FROM t WHERE id=3;

SELECT * FROM t;

DROP FUNCTION f;

DROP TABLE t;